R=120;
C=33e-12;
tau=R*C;
T=tau/300;
t=0:T:(10*tau);
N=length(t);
U(1)=0;

stdn = 3;
for k=2:N;
    E(k) = randn(1,1) * stdn;
    U(k)=U(k-1)-(T/tau)*U(k-1)+E(k)*T/(2*tau);
end;

figure(1)
plot(t,E,t,U)